Air conditioning system with ice storage

ABSTRACT

An air conditioning system includes a condenser and an evaporator configured to remove thermal energy from a water flow through the evaporator via a refrigerant flow through the evaporator. A refrigerant conduit is configured to convey a refrigerant flow through the evaporator and the condenser. An ice storage tank is fluidly connected to the refrigerant conduit such that the refrigerant flow is flowable through the ice storage tank to transfer thermal energy between the refrigerant flow and a volume of frozen water disposed in the ice storage tank.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to air conditioning systems. More specifically, the subject disclosure relates ice storage systems for air conditioning systems.

Ice storage is used in air conditioning systems, for example, chiller systems, to take advantage of the large energy content of a volume of frozen water. A traditional ice storage system for an air conditioning system 100 is shown in FIG. 1. In the air conditioning system 100, refrigerant is circulated in a refrigerant loop 102 which flows the refrigerant through a typical refrigerant cycle including a compressor 104, a condenser 106, an expansion valve 108, and an evaporator 110. A brine loop 112 also passes through the evaporator 110 such that the evaporator 110 acts as a brine cooler during operation of the air conditioning system 100. The brine loop 112 passes through an ice storage tank 114, typically with one or more valves 116 to direct the brine flow, a typical brine is an ethylene glycol solution, through the brine loop 112.

Such a system operates in many different modes depending on cooling requirements. In brine cooling mode, also called vapor compression mode, the chiller 100 operates as a conventional chiller. The valves 116 are closed and/or opened so that the brine flow bypasses the ice storage tank 114 and flows through the evaporator 110. In this mode, the evaporator 110 cools the brine flow to about 7 degrees Celsius and the brine is flowed to a chiller 118 to cool a desired space. When the system 100 is operating in ice storage mode, such as when there is not a need to cool the desired space, the air conditioning system 100 flows the brine not to the chiller 118, but to the ice storage tank 114. During this mode, the brine is cooled to −5 degrees to −10 degrees Celsius by the evaporator 110 and freezes water in the ice storage tank 114 thus storing cooling energy in the ice storage tank 114. During operation of the air conditioning system 100 in ice cooling mode, the refrigerant loop 102 is not operating. Brine is circulated through the ice storage tank 114 to cool the brine flow which is then flowed to the chiller 118 to cool the desired space.

Use of the ice storage tank 114 in conjunction with the chiller 118 allows a size of the chiller 118 and allows the air conditioning system 100 to take advantage of lower nighttime electricity costs by using ice storage mode.

Circulation of brine through the ice storage tank 114, however, reduces thermal efficiency of the air conditioning system 100 versus a system utilizing water routed through the chiller 118, since brine has poor heat transfer characteristics when compared to water. Further, inclusion of the brine loop 112 makes the air conditioning system 100 layout complicated due to the valves 116 and other components required to direct the brine flow through the system when operating in the various modes.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, an air conditioning system includes a condenser and an evaporator configured to remove thermal energy from a water flow through the evaporator via a refrigerant flow through the evaporator. A refrigerant conduit is configured to convey a refrigerant flow through the evaporator and the condenser. An ice storage tank is fluidly connected to the refrigerant conduit such that the refrigerant flow is flowable through the ice storage tank to transfer thermal energy between the refrigerant flow and a volume of frozen water disposed in the ice storage tank.

According to another aspect of the invention, a method of operating an air conditioning system includes urging a refrigerant flow along a refrigerant pathway and through a compressor. The refrigerant flow is conveyed through a condenser disposed along the refrigerant pathway and at least a portion of the refrigerant flow is flowed through an ice storage tank via an ice tank pathway. A volume of water disposed in the ice storage tank is frozen via the refrigerant flow thus storing cooling energy in the ice storage tank.

According to yet another aspect of the invention, a method of operating an air conditioning system includes conveying a refrigerant flow through a refrigerant conduit to an ice storage tank, the ice storage tank containing a volume of frozen water therein. Thermal energy is transferred from the refrigerant flow to the volume of frozen water, thereby cooling the refrigerant flow. The refrigerant flow is urged from the ice storage tank to an evaporator and a water flow is conveyed to the evaporator via a water pathway. Thermal energy is transferred from the water flow to the refrigerant flow via the evaporator, thereby cooling the water flow. The water flow is conveyed to a chiller to cool a desired space via the chiller.

These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of a typical air conditioning system including ice storage;

FIG. 2 is a schematic of an embodiment of an improved air conditioning system;

FIG. 3 is a schematic of an embodiment of an air conditioning system operating in vapor compression mode;

FIG. 4 is a schematic of an embodiment of an air conditioning system operating in ice storage mode;

FIG. 5 is a schematic of an embodiment of an air conditioning system operating in ice cooling mode; and

FIG. 6 is a schematic of an embodiment of an air conditioning system operating an alternative cooling mode;

The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

Shown in FIG. 2 is an improved air conditioning system 200. In the air conditioning system 200, refrigerant is circulated in a refrigerant pathway 202 which flows the refrigerant through a typical refrigerant cycle including a compressor 204, a condenser 206, an expansion valve 208, and an evaporator 210. A direct-expansion ice storage tank 212 is connected to the refrigerant conduit 202 via an ice tank pathway 214. The ice tank pathway 214 is connected to the refrigerant conduit 202 by one or more control valves 216. A refrigerant pump 218 may be located along the ice tank conduit 214. The evaporator 210 cools a flow of water which is circulated through a water pathway 220 through the evaporator 210 and to a chiller 222 which cools a desired space 224 via the flow of water. While the ice storage tank 212 is shown in FIG. 2 to be located outside of the chiller 222, in some embodiments the ice storage tank 212 may be disposed internal to the chiller 222. As will be explained in more detail below, the air conditioning system 200 eliminates the brine loop of the prior art resulting in a more efficient and less complex operation of the air conditioning system 200 versus that of the prior art.

The air conditioning system 200 operates in a variety of modes depending on cooling requirements of the space 224. Shown in FIG. 3 is operation of the air conditioning system 200 in vapor compression, or water cooling mode. In this mode, the refrigerant flow (as shown by the dashed lines in FIG. 3) is circulated through the refrigerant pathway 202 as in a traditional air conditioning system. In this mode, the refrigerant flow passing through the evaporator 210 absorbs thermal energy from the water flow passing through the evaporator 210.

Illustrated in FIG. 4 is operation of the air conditioning system 200 in ice storage mode. At times where it is advantageous to do so, such as off-peak hours where electricity cost is reduced and/or cooling needs are lower, the system can be operated in ice storage mode to freeze water, or other phase change material, in the ice storage tank 212 thus “storing” an amount of cooling energy in the ice storage tank 212 for use at a later time. In ice storage mode, a control valve 216 is opened between the refrigerant pathway 202 and the ice tank pathway 214 and the expansion valve 208 is closed. This diverts the refrigerant flow from the condenser 206 through the control valve 216 and through the ice storage tank 212 via the ice tank pathway 214. As the refrigerant flow (shown again by the dashed lines in FIG. 4) passes through the ice storage tank 212 at about −3 to −7 degrees Celsius, the water in the ice storage tank 212 is frozen. The refrigerant flow leaving the ice storage tank 212 is returned to the compressor 204. In some embodiments, the refrigerant flow bypasses the evaporator 210 when the system 200 is operating in ice storage mode.

The stored cooling energy in the ice storage tank 212 is utilized when the system 200 is operated in ice cooling mode illustrated in FIG. 5. In this mode, the compressor 204, condenser 206 an expansion valve 208 are all turned “off”. As such, the refrigerant (shown by dashed lines in FIG. 5) is circulated between the evaporator and the ice storage tank 212. The refrigerant flow naturally seeks the lowest temperature portion of the system 200, which in this mode is the ice storage tank 212, so it is not necessary to pump the refrigerant to the ice storage tank 212. The refrigerant flows through the ice storage tank 212 where it is cooled, changing the phase from gas to liquid and pumped in liquid phase from the ice storage tank 212 via the refrigerant pump 218. The cooled refrigerant then flows through the evaporator 210 where thermal energy from the water flowing through the water pathway 220 is absorbed by the refrigerant flow thereby cooling the water flow. The water flow is then circulated to the chiller 222 via the water pathway 220. The refrigerant is evaporated while absorbing a heat from water and in gas phase flow from the evaporator 210 bypasses the compressor 204, condenser 206 and expansion valve 208 via a bypass pathway 226 and returns to the ice storage tank 212.

The system 200 can also be operated in a dual water cooling and ice cooling mode. In this mode, as shown in FIG. 6, the compressor 204, condenser 206 and expansion valve 208 are turned “on”, but the valve 216 is closed. Refrigerant (shown as the dashed lines in FIG. 6) circulates through both the refrigerant pathway 202 and the ice tank pathway 214, with a portion of the refrigerant bypassing the compressor 204 and flowing to the ice storage tank 212 via the bypass pathway 226. The refrigerant portion flowing through the ice storage tank 212 is cooled by the ice stored therein while the refrigerant portion flowing into the compressor 204 is cooled via the compressor 204, condenser 206 and expansion valve 208.

While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims. 

1. An air conditioning system comprising: a condenser; an evaporator configured to remove thermal energy from a water flow through the evaporator via a refrigerant flow through the evaporator; a refrigerant conduit configured to convey a refrigerant flow through the evaporator and the condenser; and an ice storage tank fluidly connected to the refrigerant conduit such that the refrigerant flow is flowable through the ice storage tank to transfer thermal energy between the refrigerant flow and a volume of frozen water disposed in the ice storage tank.
 2. The air conditioning system of claim 1, wherein the ice storage tank is disposed external to a chiller of the air conditioning system.
 3. The air conditioning system of claim 1, further comprising a pump configured to urge the refrigerant flow from the ice storage tank to the evaporator.
 4. The air conditioning system of claim 1, further comprising an ice tank conduit extending through the ice storage tank configured to convey the refrigerant flow through the ice storage tank.
 5. The air conditioning system of claim 4, wherein the ice tank conduit is connected to the refrigerant conduit via one or more valves.
 6. The air conditioning system of claim 5, wherein opening the one or more valves allows the refrigerant flow to flow through the ice storage tank.
 7. The air conditioning system of claim 1, wherein the water flow is urged from the evaporator to a chiller to cool a desired space.
 8. A method of operating an air conditioning system comprising: urging a refrigerant flow along a refrigerant pathway and through a compressor; conveying the refrigerant flow through a condenser disposed along the refrigerant pathway; flowing at least a portion of the refrigerant flow through an ice storage tank via an ice tank pathway; and freezing a volume of phase change material disposed in the ice storage tank via the refrigerant flow thus storing cooling energy in the ice storage tank.
 9. The method of claim 8, wherein a refrigerant flow temperature is about −3.0 to −7.0 degrees Celsius below a freezing point of the phase change material.
 10. The method of claim 8, further comprising opening at least one valve between the refrigerant pathway and the ice tank pathway to allow the refrigerant flow to flow to the ice storage tank.
 11. The method of claim 8, further comprising: flowing at least a portion of the refrigerant flow from the condenser to an evaporator; transferring thermal energy from a water flow to the refrigerant flow thus cooling the water flow, the water flow flowing through the evaporator via a water pathway; conveying the water flow to a chiller via the water pathway; and cooling a desired space via the chiller.
 12. A method of operating an air conditioning system comprises: conveying a refrigerant flow through a refrigerant conduit to an ice storage tank, the ice storage tank containing a volume of frozen phase change material therein; transferring thermal energy from the refrigerant flow to the volume of frozen phase change material, thereby cooling the refrigerant flow; urging the refrigerant flow from the ice storage tank to an evaporator; conveying a water flow to the evaporator via a water pathway; transferring thermal energy from the water flow to the refrigerant flow via the evaporator, thereby cooling the water flow; and conveying the water flow to a chiller to cool a desired space via the chiller.
 13. The method of claim 12, wherein a temperature of the ice storage tank is lower than a refrigerant temperature, thus the refrigerant flow is conveyed to the ice storage tank via thermal forces.
 14. The method of claim 12, wherein the refrigerant flow is urged from the ice storage tank to the evaporator via a pump.
 15. The method of claim 12, wherein the refrigerant flow bypasses a compressor, a condenser, and/or an expansion valve disposed along the refrigerant pathway.
 16. The method of claim 12, wherein a refrigerant flow temperature is about −3.0 to −7.0 degrees Celsius below a freezing point of the phase change material. 